1. Field of the Invention
The present invention relates to a surface-mount type switching power-supply unit provided with a switching power-supply circuit of an isolation type having a transformer and a mounting method for the same.
2. Description of the Related Art
A surface-mount type switching power-supply unit is designed in modules in such a way that, for example, a switching power-supply circuit made up of an AC-DC converter, a DC—DC converter, an inverter, etc., is constructed by forming a plurality of circuit components, wiring patterns, etc., on a circuit board. Such a switching power-supply unit is surface mounted, for example, on a mother board. When the above switching power-supply unit is surface mounted on the mother board, for example, first of all, the above switching power-supply unit is held by a suction nozzle, the switching power-supply unit is transferred to the mother board by the suction nozzle, and then the switching power-supply unit is surface mounted on the mother board by reflowing welding, etc.
When the switching power-supply unit is transferred by the suction nozzle, in order to prevent problems such as dropping the switching power-supply unit from the suction nozzle, etc., a broad and flat surface for suction by the above suction nozzle is required on the switching power-supply unit. In the prior art, for example, the whole of a switching power-supply unit is covered by a case and transfer molding takes place as shown in FIG. 5. That is, the whole switching power-supply unit is transfer molded and a broad and flat surface for the suction nozzle is secured in the upper portion of the switching power-supply unit.
However, when such a transfer molding takes place, because a case covering all the components of a switching power-supply circuit on the upper side of a switching power-supply unit is provided with a spacing between the case and all the components, a problem of heightening the switching power-supply unit arises, and accordingly, measures to produce low-profile products cannot be fully taken. Moreover, high costs for the transfer molding are needed, and then a problem of increasing the cost of the switching power-supply units also arises.